In thalassemia, both increased iron alimentary absorption and repeated transfusions can cause iron overload. These iron deposits may occur in many organs and tissues in the body with deleterious effects on the patient's health. In the research leading to improved clinical management of Thalassemia major, methods of reducing iron burdens by chelation therapy are being investigated. These studies have been hampered by the lack of a sensitive quantitative measure of body stores of iron. The following proposal offers a unique quantitative, non-invasive measure of iron deposits to be applied in the above chelation therapy programs in order to evaluate quantitatively their effectiveness. The quantification of body stores of iron rests on a newly developed technique of nuclear resonance scattering. In this technique, the nucleus of 56Fe (92% isotopic abundance) is raised to its first excited state by gamma radiation. The excited nucleus decays to ground state by emission of the 847 KeV gamma-ray. This gamma ray is measured by special detection instrumentation. A prototype instrument to measure small amounts of iron has been constructed and used in phantom studies. These studies clearly indicate the feasibility of this technique for measuring tissue deposited iron. This project will build a full scale instrument capable of measuring low levels of iron in the heart and liver of Thalassemic patients. The calibration and testing of this NRS facility will complete phase 1. In phase 2, this facility will be used to measure changes in iron deposits in Thalassemic patients currently undergoing chelation therapy in research studies in the New York area. Patients will be brought to Brookhaven at 6-12 month intervals for this measurement.